Power converter with controller operable in selected modes of operation

Abstract

A power converter and method of controlling the same for selected modes of operation. In one embodiment, the power converter includes a first power switch coupled to a source of electrical power and a second power switch coupled to the first power switch and to an output terminal of the power converter. The power converter also includes a controller configured to control an operation of the first and second power switches during selected modes of operation.

What is claimed is: 
     
       1. A controller for use with a circuit having first and second switches operable in a mode of operation, configured to:
 alternately enable conduction of said first and second switches with primary and complementary duty cycles, respectively, in response to an output characteristic of said circuit during a switching cycle, said first switch configured to couple an output inductor to an input of said circuit and said second switch configured to couple said output inductor across output terminals of said circuit; and 
 disable conduction of said second switch when a current associated with said second switch is less than a current threshold level, said current threshold level being a fixed level selected to prevent reverse current flow in an inductor current through said output inductor and adjusted with a resistor divider network coupled to a positive bias voltage source and a negative bias voltage source, said current associated with said second switch being one of a second switch current and said inductor current through said output inductor of said circuit. 
 
     
     
       2. The controller as recited in  claim 1  wherein said resistor divider network is configured to divide a voltage difference between said positive bias voltage source and said negative bias voltage source. 
     
     
       3. The controller as recited in  claim 1  wherein said resistor divider network includes an external resistor. 
     
     
       4. The controller as recited in  claim 1  wherein said current associated with said second switch is an instantaneous current. 
     
     
       5. The controller as recited in  claim 1  wherein said controller is configured to control a level of current of said first switch during said complementary duty cycle. 
     
     
       6. The controller as recited in  claim 1  wherein said circuit is operable in another mode of operation when said current associated with said second switch is less than said current threshold level and said controller is configured to alternately enable conduction of said first and second switches with primary and complementary duty cycles, respectively, in response to said output characteristic of said circuit during said switching cycle and control a level of current of said first switch when said alternately enabling conduction of said first and second switched is disabled. 
     
     
       7. The controller as recited in  claim 6  wherein said controller is configured to disable elements therein during said another mode of operation. 
     
     
       8. The controller as recited in  claim 1  wherein said controller is configured to limit said complementary duty cycle when a switching cycle counter exceeds a predetermined count. 
     
     
       9. The controller as recited in  claim 1  wherein said output characteristic is an output voltage of said circuit. 
     
     
       10. A method for use with a circuit having first and second switches operable in a mode of operation, comprising:
 alternately enabling conduction of said first and second switches with primary and complementary duty cycles, respectively, in response to an output characteristic of said circuit during a switching cycle, said first switch configured to couple an output inductor to an input of said circuit and said second switch configured to couple said output inductor across output terminals of said circuit; and 
 disabling conduction of said second switch when a current associated with said second switch is less than a current threshold level, said current threshold level being a fixed level selected to prevent reverse current flow in an inductor current through said output inductor and adjusted with a resistor divider network coupled to a positive bias voltage source and a negative bias voltage source, said current associated with said second switch being one of a second switch current and said inductor current through said output inductor of said circuit. 
 
     
     
       11. The method as recited in  claim 10  wherein said resistor divider network divides a voltage difference between said positive bias voltage source and said negative bias voltage source. 
     
     
       12. The method as recited in  claim 10  wherein said resistor divider network includes an external resistor. 
     
     
       13. The method as recited in  claim 10  wherein said current associated with said second switch is an instantaneous current. 
     
     
       14. The method as recited in  claim 10  further comprising controlling a level of current of said first switch during said complementary duty cycle. 
     
     
       15. The method as recited in  claim 10  wherein said circuit is operable in another mode of operation when said current associated with said second switch is less than said current threshold level, said method further comprising alternately enabling conduction of said first and second switches with primary and complementary duty cycles, respectively, in response to said output characteristic of said circuit during said switching cycle and controlling a level of current of said first switch when said alternately enabling conduction of said first and second switched is disabled. 
     
     
       16. The method as recited in  claim 15  further comprising disabling elements during said another mode of operation. 
     
     
       17. The method as recited in  claim 10  further comprising limiting said complementary duty cycle when a switching cycle counter exceeds a predetermined count. 
     
     
       18. The method as recited in  claim 10  wherein said output characteristic is an output voltage of said circuit.